The present invention relates to a device for controlling the service loads of an electric household appliance, in particular a refrigerator.
As is known, many household appliances require systems for regulating and controlling one or more operating functions, which are activated or deactivated according to various operating conditions. Such is the case, for example, of a refrigerator compressor, which calls for a control system which, in response to temperature variations measured inside the refrigerator, turns the compressor on or off under the control, for example, of a mechanical thermostat. The compressor supply circuit normally comprises two activating branches, which are active at the start-up (or xe2x80x9claunchxe2x80x9d) stage and the normal running (xe2x80x9coperatingxe2x80x9d) stage respectively: in which case, a positive temperature coefficient PTC resisting unit is used to regulate current flow through the launch branch, and the mechanical thermostat for regulating current flow through the operating branch.
A major drawback of control systems of this type is the relatively high energy consumption involved, which is mainly due to the presence of the continuously operating PTC unit, and to the difficulty in regulating the mechanical thermostat.
Employing an electronic as opposed to mechanical thermostat and other types of relays in place of PTC units permits a certain, albeit relatively small, reduction in consumption, but calls for the use of more complex, more expensive components.
It is an object of the present invention to provide a device for controlling the service loads of an electric household appliance, which, though cheap and easy to produce, provides for low-energy operation and long-term reliability.
According to the present invention, there is provided a device for controlling the service loads of an electric household appliance, in particular a refrigerator, comprising a control unit for controlling service functions of said electric household appliance, and a positive temperature coefficient (PTC) resisting unit connected in series with said control unit; characterized by also comprising thermally activated actuating means for selectively connecting/disconnecting respective auxiliary switches of said service loads; said PTC unit being located close to said thermally activated actuating means, and generating, when supplied with electric current, sufficient heat to activate said thermally activated actuating means.
Said PTC unit used to thermally activate said actuating means is advantageously the same one used to directly regulate operation of at least one power application of said electric household appliance.
More specifically, said thermally activated actuating means comprise at least one temperature-deformable element; at least one movable control member for controlling said auxiliary switches; and kinematic connecting means between said deformable element and said movable control member.
In a preferred embodiment, the movable control member is a camshaft, the cams of which cooperate with said respective auxiliary switches of said loads to selectively connect/disconnect the auxiliary switches; at least one cam of said camshaft is also used to determine the angular position of the camshaft.
The device according to the invention preferably also comprises a control circuit for controlling the PTC unit and for cyclically cutting off supply to the PTC unit, e.g. by means of an electronic switch interposed between the control unit and the PTC unit, once sufficient heat has been generated by the PTC unit to activate said thermally activated actuating means.
The device according to the invention is therefore straightforward and reliable, does not call for particularly complex and/or high-cost components, and, as compared with known control systems, provides for significant in-service energy saving. Supply to the PTC unit, in fact, may be cut off at the end of each cycle to activate the service load (or loads), thus reducing overall consumption of the device. The device according to the invention is also highly flexible, by controlling and regulating numerous different service functions of the electric household appliance to which it is applied. For example, in the case of a refrigerator, in addition to the compressor, the device may also control the interior light, the fan, etc., and this using only one PTC unit, in particular, the same one used to control operation of the compressor. For which purpose, in fact, the movable control member need simply be provided with a number of cams for controlling corresponding switches for the various loads. One or more cams may also advantageously be used to determine the angular position of the movable control member, so that the control unit is always in a condition to determine the position of the movable control member and, hence, the operating conditions of the system, and may also intervene in the event of failure to activate any of the service functions.
Moreover, the device according to the invention enables all the heat-generating components to be located as best suited to the application in question. More specifically, in the case of a refrigerator, such components may be located away from the code region, e.g. directly on the compressor, thus improving the overall efficiency of the appliance.